Home entertainment systems are proposed capable of playing back moving images as well as running game programs. In home entertainment systems, a GPU generates three-dimensional images using polygons (see, for example, patent document No. 1).
Regardless of the purpose of image display, improvement in efficiency of displaying images is an important and constant challenge. High-speed rendering of high-definition images requires various efforts. For example, there is proposed a method of storing texture data separately to make the process of mapping efficient (e.g., non-patent document Nos. 1 and 2).    [patent document 1] U.S. Pat. No. 6,563,999    [non-patent document 1] Sylvain Fefebvre, et. al., Unified Texture Management for Arbitrary Meshes, Repport de recherche, N5210, May 2004, Institut National De Recherche En Informatique Et En Automatique    [non-patent document 2] Martin Kraus, et. al., Adaptive Texture Maps, Graphics Hardware (2002), pp 1-10, The Eurographics Association
For responsive display of high-definition images, reduction in data size and high-speed rendering are important and constant challenges. When a need arises to update a part of an image, complex processes of, for example, totally updating the data structure once built are likely to be required, even if the above-mentioned approach of devising a data structure (e.g., texture mapping) is used.